A superconducting magnet device that generates a high magnetic field using a superconducting coil in a superconducting state has conventionally been known. For example, JP 2013-74082 A discloses a superconducting magnet device including a superconducting coil, a radiation shield housing the superconducting coil, a vacuum case housing the radiation shield, an electrode pin connected to the vacuum case, a conductive member (e.g., a copper wire) for connecting the superconducting coil to the electrode pin, and a refrigeration unit connected to the vacuum case to refrigerate the superconducting coil. The conductive member includes an oxidized lead disposed inside the radiation shield. The oxidized lead is a conductor capable of conducting electricity from the electrode pin to the superconducting coil while minimizing heat transfer into the superconducting coil from the outside. The oxidized lead is connected to the superconducting coil and the electrode pin via conductive wires.
In the superconducting magnet device as disclosed in JP 2013-74082 A, the oxidized lead might burn out due to such a cause as a current flow in the insufficiently cooled oxidized lead. If such a burn out occurs, the oxidized lead needs to be replaced, and the replacement is very complicated. Specifically, to expose the oxidized lead to the outside, at least the vacuum case needs to be cut and the refrigeration unit and the radiation shield need to be removed. Then, after replacing the oxidized lead, the radiation shield should be reconnected, the refrigeration unit be reassembled, and the vacuum case be reconnected. As can be understood, replacement of the oxidized lead is very complicated and difficult to do at a site where the superconducting magnet device is installed. Therefore, the superconducting magnet device is transported from the site to a factory (where the replacement of the oxidized lead can be done), and then the replacement of the oxidized lead is done in the factory.
This means that if the oxidized lead burns out, a long downtime of the superconducting magnet device is required since the superconducting magnet device should be transported from the site to the factory to replace the oxidized lead in the factory, and then the superconducting magnet device should be sent back to the site. Moreover, if peripheral apparatuses are installed around the superconducting magnet device, the peripheral apparatuses should be disassembled and re-installed, which further extends the downtime of the device.